Error "error code (204)" when trying to activate my Sage 200 licence in System Administrator

"error code (204). Invalid entitlement file error, your licence is not valid" when trying to activate Sage 200 licence in System Administrator, information on how to correct this issue.

This normally relates to http activation not being installed
or
you may need to run the batch file for WSUS option D per the Deployment and Installation Guide. This guide is available on my.sage.co.uk.

In addition, some have found that they need to run the fixes out of this article.